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76 THE CONDOR Vol. XIV of flowers among which they dan disport themselves and from which they sect?re the nectar and small insects which compose most of their food supply. Unlike the Black-chinned Hummingbird or their larger cousin, the Anna Hummingbird, they seem to enjoy each other's company, and. it is nothing unusual to find them almost in colonies, as many as five nests being located in a radius of fifty feet in an unusually well sit- uated grove of oaks. For the most part they are quiet; but prior to the nesting season a short time are quite noisy, chasing each other up, down and around through the surrounding bushes and trees. Their note consists of a few sharp squeaks, given out more often when in very rapid flight than otherwise. During the breeding season the male has a very peculiar way of disporting himself before the female. When he locates his mate sitting on a tree, or more often on a low bush, he will ascend to an elevation of about one hundred feet and t6 one side of the female and will then turn and swoop down at a fearful speed, passing perhaps within a few inches of the watching female and ascending in the air to complete a half circle. This he keeps up until the female becomes impatient and endeavors to escape; then perhaps all that Fig. 27. FEMALE COSTA HUMMINGBIRD; NEST IN LEMON- TREE AT ESCONDIDO, APRIL, 1911 one will see is a streak, and a sharp squeak or two is heard as they flash up the hillside. The noise that the male makes in doing his fancy dive is easily heard at some distance and quite often heard when the bird himself is not visible on account of the extreme speed at which he travels on his downward plunge. For nesting places Costa Hummingbirds most commonly select some bush on a cliff. or steep bank on a hillside, but they are also to be found nesting in the orange and lemon groves, in olive trees, in dead cockle burrs in a river bottom or in dead trees; in fact they seem to prefer a dead limb rather than a live one for a nesting site. I think that is due to the fact that the nesting material they use harmonizes better with the dead branches. The nest is made of plant down and weed leaves principally, bound together with cob- webs and lined with plant down and an occasional feather. A typical nest measures: inside depth, one half inch; outside depth, one and one-quarter inches; inside diameter, three- fourths of an inch; outside diameter, one and one-half inches. The female selects the nest- ing site and as far as I have observed, does all the work on it, also all of the incubating, the